/*
** $Id: llimits.h $
** 限制，基础类型和一些其他的安装依赖定义
** See Copyright Notice in lua.h
*/

#ifndef llimits_h
#define llimits_h


#include <limits.h>
#include <stddef.h>


#include "lua.h"


/*
** 'lu_mem' 和 'l_mem' 是足够去统计Lua使用的总内存的 unsigned/signed整数，通常他们是'size_t'和'ptrdiff_t',但是在16位机器上，我们使用'long'
*/
#if defined(LUAI_MEM)		/* { external definitions? */
typedef LUAI_UMEM lu_mem;
typedef LUAI_MEM l_mem;
#elif LUAI_IS32INT	/* }{ */
typedef size_t lu_mem;
typedef ptrdiff_t l_mem;
#else  /* 16-bit ints */	/* }{ */
typedef unsigned long lu_mem;
typedef long l_mem;
#endif				/* } */


/* chars used as small naturals (so that 'char' is reserved for characters) */
typedef unsigned char lu_byte;
typedef signed char ls_byte;


/* size_t的最大值 */
#define MAX_SIZET	((size_t)(~(size_t)0))

/* Lua可见的最大尺寸(必须在lua_Integer中表示) */
#define MAX_SIZE	(sizeof(size_t) < sizeof(lua_Integer) ? MAX_SIZET \
                          : (size_t)(LUA_MAXINTEGER))


#define MAX_LUMEM	((lu_mem)(~(lu_mem)0))

#define MAX_LMEM	((l_mem)(MAX_LUMEM >> 1))


#define MAX_INT		INT_MAX


/*
** floor of the log2 of the maximum signed value for integral type 't'.
** (也就是说，最大的n使得2^n适合给定的有符号类型)
*/
#define log2maxs(t)	(sizeof(t) * 8 - 2)


/*
** 测试无符号值是否是2的次方
*/
#define ispow2(x)	(((x) & ((x) - 1)) == 0)


/* 字面字符串不包含\0的char长度 */
#define LL(x)   (sizeof(x)/sizeof(char) - 1)


/*
** 将指针转换成无符号整数: 只能用于hashing;
** there is no problem if the integer cannot hold the whole pointer
** value. (In strict ISO C this may cause undefined behavior, but no
** actual machine seems to bother.)
*/
#if !defined(LUA_USE_C89) && defined(__STDC_VERSION__) && \
    __STDC_VERSION__ >= 199901L
#include <stdint.h>
#if defined(UINTPTR_MAX)  /* even in C99 this type is optional */
#define L_P2I	uintptr_t
#else  /* no 'intptr'? */
#define L_P2I	uintmax_t  /* use the largest available integer */
#endif
#else  /* C89 option */
#define L_P2I	size_t
#endif

#define point2uint(p)	((unsigned int)((L_P2I)(p) & UINT_MAX))



/* types of 'usual argument conversions' for lua_Number and lua_Integer */
typedef LUAI_UACNUMBER l_uacNumber;
typedef LUAI_UACINT l_uacInt;


/*
** Internal assertions for in-house debugging
*/
#if defined LUAI_ASSERT
#undef NDEBUG
#include <assert.h>
#define lua_assert(c)           assert(c)
#endif

#if defined(lua_assert)
#define check_exp(c,e)		(lua_assert(c), (e))
/* to avoid problems with conditions too long */
#define lua_longassert(c)	((c) ? (void)0 : lua_assert(0))
#else
#define lua_assert(c)		((void)0)
#define check_exp(c,e)		(e)
#define lua_longassert(c)	((void)0)
#endif

/*
** 用于检测 API 调用的断言
*/
#if !defined(luai_apicheck)
#define luai_apicheck(l,e)	((void)l, lua_assert(e))
#endif

#define api_check(l,e,msg)	luai_apicheck(l,(e) && msg)


/* 用于避免警告(无实际含义) */
#if !defined(UNUSED)
#define UNUSED(x)	((void)(x))
#endif


/* 类型转换 */
#define cast(t, exp)	((t)(exp))

#define cast_void(i)	cast(void, (i))
#define cast_voidp(i)	cast(void *, (i))
#define cast_num(i)	cast(lua_Number, (i))
#define cast_int(i)	cast(int, (i))
#define cast_uint(i)	cast(unsigned int, (i))
#define cast_byte(i)	cast(lu_byte, (i))
#define cast_uchar(i)	cast(unsigned char, (i))
#define cast_char(i)	cast(char, (i))
#define cast_charp(i)	cast(char *, (i))
#define cast_sizet(i)	cast(size_t, (i))


/* 转换 lua_Integer -> lua_Unsigned */
#if !defined(l_castS2U)
#define l_castS2U(i)	((lua_Unsigned)(i))
#endif

/*
** 转换lua_Unsigned -> signed lua_Integer; 
*/
#if !defined(l_castU2S)
#define l_castU2S(i)	((lua_Integer)(i))
#endif


/*
** non-return type
*/
#if !defined(l_noret)

#if defined(__GNUC__)
#define l_noret		void __attribute__((noreturn))
#elif defined(_MSC_VER) && _MSC_VER >= 1200
#define l_noret		void __declspec(noreturn)
#else
#define l_noret		void
#endif

#endif


/*
** Inline functions
*/
#if !defined(LUA_USE_C89)
#define l_inline	inline
#elif defined(__GNUC__)
#define l_inline	__inline__
#else
#define l_inline	/* empty */
#endif

#define l_sinline	static l_inline


/*
** 虚拟机指令类型;
** must be an unsigned with (at least) 4 bytes (see details in lopcodes.h)
*/
#if LUAI_IS32INT
typedef unsigned int l_uint32;
#else
typedef unsigned long l_uint32;
#endif

typedef l_uint32 Instruction;



/*
** 短字符串的最大长度(不能小于保留字和元方法名)
** #("function") = 8, #("__newindex") = 10.)
*/
#if !defined(LUAI_MAXSHORTLEN)
#define LUAI_MAXSHORTLEN	40
#endif


/*
** 字符串表的初始化大小(必须是2的次方).仅Lua核心就注册了大约50个字符串(保留字+元事件键+其他一些)
*/
#if !defined(MINSTRTABSIZE)
#define MINSTRTABSIZE	128
#endif


/*
** API中的字符串缓存大小，“N”是集合的数量(最好是素数)，“M”是每个集合的大小(M == 1表示直接缓存)。
*/
#if !defined(STRCACHE_N)
#define STRCACHE_N		53
#define STRCACHE_M		2
#endif


/* string buffer的最小尺寸 */
#if !defined(LUA_MINBUFFER)
#define LUA_MINBUFFER	32
#endif


/*
** 嵌套 C 调用的最大深度,语法嵌套的非终结符，以及通过C递归实现的其他特性。
** (Value must fit in a 16-bit unsigned integer. It must also be compatible with the size of the C stack.)
*/
#if !defined(LUAI_MAXCCALLS)
#define LUAI_MAXCCALLS		200
#endif


/*
** 每当程序进入Lua的核心时执行lua_lock, 离开时执行lua_unlock
*/
#if !defined(lua_lock)
#define lua_lock(L)	((void) 0)
#define lua_unlock(L)	((void) 0)
#endif

/*
** macro executed during Lua functions at points where the function can yield.
*/
#if !defined(luai_threadyield)
#define luai_threadyield(L)	{lua_unlock(L); lua_lock(L);}
#endif


/*
** 这些宏允许用户在线程created/deleted/resumed/yielded时执行指定操作
*/
#if !defined(luai_userstateopen)
#define luai_userstateopen(L)		((void)L)
#endif

#if !defined(luai_userstateclose)
#define luai_userstateclose(L)		((void)L)
#endif

#if !defined(luai_userstatethread)
#define luai_userstatethread(L,L1)	((void)L)
#endif

#if !defined(luai_userstatefree)
#define luai_userstatefree(L,L1)	((void)L)
#endif

#if !defined(luai_userstateresume)
#define luai_userstateresume(L,n)	((void)L)
#endif

#if !defined(luai_userstateyield)
#define luai_userstateyield(L,n)	((void)L)
#endif



/*
** luai_num*定义了一些数字的基本操作
*/

/* 向下取余除法 (定义为 'floor(a/b)') */
#if !defined(luai_numidiv)
#define luai_numidiv(L,a,b)     ((void)L, l_floor(luai_numdiv(L,a,b)))
#endif

/* 浮点除法 */
#if !defined(luai_numdiv)
#define luai_numdiv(L,a,b)      ((a)/(b))
#endif

/*
** 取模: 定义为'a - floor(a/b)*b';
** 使用这个定义的直接计算有几个舍入误差的问题，所以最好使用'fmod'。
** 'fmod' 给出 'a - trunc(a/b)*b' 的结果, 因此必须在 'trunc(a/b) ~= floor(a/b)' 时纠正它。
** 这发生在除法中有一个非整数的负数结果时非正数的结果等于一个非零余数'm'；负数结果也就是 'a' 和 'b'符号不同，或 'm' 和 'b' 符号不同('fmod' 的结果 ’m' 和 'a' 符号一致)
*/
#if !defined(luai_nummod)
#define luai_nummod(L,a,b,m)  \
  { (void)L; (m) = l_mathop(fmod)(a,b); \
    if (((m) > 0) ? (b) < 0 : ((m) < 0 && (b) > 0)) (m) += (b); }
#endif

/* 幂 */
#if !defined(luai_numpow)
#define luai_numpow(L,a,b)  \
  ((void)L, (b == 2) ? (a)*(a) : l_mathop(pow)(a,b))
#endif

/* the others are quite standard operations */
#if !defined(luai_numadd)
#define luai_numadd(L,a,b)      ((a)+(b))
#define luai_numsub(L,a,b)      ((a)-(b))
#define luai_nummul(L,a,b)      ((a)*(b))
#define luai_numunm(L,a)        (-(a))
#define luai_numeq(a,b)         ((a)==(b))
#define luai_numlt(a,b)         ((a)<(b))
#define luai_numle(a,b)         ((a)<=(b))
#define luai_numgt(a,b)         ((a)>(b))
#define luai_numge(a,b)         ((a)>=(b))
// a != a 那么这个数字就是NAN了
#define luai_numisnan(a)        (!luai_numeq((a), (a)))
#endif





/*
** 用于控制堆栈重新分配中一些硬测试
*/
#if !defined(HARDSTACKTESTS)
#define condmovestack(L,pre,pos)	((void)0)
#else
/* realloc stack keeping its size */
#define condmovestack(L,pre,pos)  \
  { int sz_ = stacksize(L); pre; luaD_reallocstack((L), sz_, 0); pos; }
#endif

#if !defined(HARDMEMTESTS)
#define condchangemem(L,pre,pos)	((void)0)
#else
#define condchangemem(L,pre,pos)  \
	{ if (gcrunning(G(L))) { pre; luaC_fullgc(L, 0); pos; } }
#endif

#endif
